Towards real-time optical measurement of microbubble content in hydrodynamic test facilities

Real-time measurement of microbubble concentrations is desirable in order to inform experimental results, particularly in studies of cavitation physics. To develop these capabilities a controlled experiment using a micro-fluidic T-junction to produce mono-disperse microbubbles was devised with the size and frequency of microbubbles measured using a line-scan camera capable of acquiring 45k images per second. Measurements were able to be obtained and reported in under 3 seconds from the triggering time. Tests were carried out in quiescent water and implementation in non-stationary environments would extend the operational range. The principal operating mode produced microbubbles on the order of 80 to 130 µm in size at frequencies ranging from 750 to 3200 bubbles per second across the range of air and water pressures tested.